Scientists have 3D-printed hair follicles in human skin tissue cultured in the lab. This marks the first time researchers have used the technology to generate hair follicles, which play an important role in skin healing and function. When it comes to engineering human skin, hair may at first seem superfluous. However, hair follicles are quite important: They produce sweat, helping regulate body temperature, and they contain stem cells that help skin heal. The finding has potential applications in regenerative medicine and drug testing, though engineering skin grafts that grow hair are still several years away.